The wetting behavior of a dental impression material relative to saliva is one of the critical parameters in respect of the accuracy of the dental impression which is obtained. Conventional impression materials, for example impression materials based on polydimethylsiloxane have, however, an inadequate wetting behavior relative to aqueous media, so that in some cases, contact angles of 90° and more result. Therefore, in order to optimize the surface affinity of dental impression materials in a hydrophilic environment, surfactant additives have been proposed and used for many years.
U.S. Pat. No. 4,657,959 discloses curable silicone compositions which contain a surfactant, in particular a fluorosurfactant as dental impression materials. If a drop of water is dripped onto the surface of such an impression material, according to the US document a contact angle of less than 10° is obtained after three minutes.
EP 1 290 998 B1 discloses a composition for dental impression based on addition-crosslinking organopolysiloxanes, where the composition contains a non-ionic surfactant and/or a polyether-modified silicone oil.
WO 2004/058 196 A1 discloses a dental impression material based on polyvinylsiloxane, in which by using a non-ionic surfactant, in particular PEG8 Methicone, a contact angle of less than 10° is to be achieved within 15 seconds, 15 minutes after curing. However, such a wetting behavior is only relevant for the surface affinity in the case of a plaster cast, but not for taking impressions in a patient's mouth.
EP 0 729 341 B1 relates to a dental impression material which contains polyethercarbosilanes for hydrophilization. In this case, contact angles of only 42° or more are achieved.
EP 0 231 420 B1 describes the hydrophilization of a dental impression material based on addition-crosslinking silicones by silicone polyether.
Furthermore, U.S. Pat. No. 5,064,891 A discloses a dental impression material containing a surfactant.
U.S. Pat. No. 5,907,002 A describes dental impression compositions which contain a non-ionic surfactant. Polyoxyethylene alkyl ether, polyoxypropylene alkyl ether, polyoxyethylene alkyl phenylether and various fatty acid esters and fluoroalkylethylene oxide surfactants are given as examples of non-ionic surfactants.
DE 199 22 929 A1 and the corresponding U.S. Pat. No. 6,291,546 B1 describes compositions containing one or more non-ionic surfactants for taking dental impressions of the oral mucosa. Polyoxyethylene alkyl ether, polyoxypropylene alkyl ether, polyoxyethylene alkyl phenylether, in particular polyoxyethylene nonylphenyl ether and various fatty acid esters and fluoroalkylethylene oxide surfactants are given as examples of non-ionic surfactants. Compositions comprising any of said ethers as well as a fluorosurfactant are not disclosed.
DE 10 2006 001 126 A1 describes compositions for dental impression materials which, in addition to a curable polymer, also contain at least one non-ionic surfactant with a molar mass of less than 6000 g/mol which has a (poly)alkylene oxide radical and a silicon-containing group (hereafter called a silicon-containing surfactant) and at least one non-ionic fluorosurfactant which has a (poly)alkylene oxide radical and at least one partially or perfluorinated hydrocarbon radical which is connected to the (poly)alkylene oxide radical via an oxygen atom or an ester group (hereafter called a fluorosurfactant). The weight ratio of silicon-containing surfactant to fluorosurfactant is within the range of from 100:1 to 1:100, preferably 50:1 to 1:50, more preferably 10:1 to 1:10 and particularly preferably 5:1 to 1:5. In preferred compositions, the content of silicon-containing surfactant and fluorosurfactant, based on the total mass of the composition, is in each case 0.001 to 10% by weight. In addition to the silicon-containing surfactant described above and the fluorosurfactant described above, the composition can contain further surfactants, inter alia alkyl-, aryl-, aralkyl-capped non-ionic surfactants, preferably alkyl-capped fatty alcohol ethoxylates, silicone surfactants, polyethercarbosilanes, carbosilane surfactants and fluorosurfactants which are alkyl-capped and in particular alkyl-capped fatty alcohol ethoxylates.
The dental impression materials which can be obtained from the compositions disclosed in patent application DE 10 2006 001 126 A1 are said to have an initial contact angle (measured between 3 and 10 seconds drop age, the drop of water being delivered 40 seconds after the start of the mixing of the catalyst and base components of the curable polymer system) of <10°, and during the processing time of between 0 and 3 minutes have an equilibrium contact angle of <10°. In comparative examples, compositions were also tested which contained a fluorosurfactant (0.75 or 1.5% by weight, based on the total mass of the composition) and a non-ionic alkyl-capped fatty alcohol ethoxylate surfactant with a surface tension of 29 mN/m (0.2% by weight, based on the total weight of the composition), but no silicon-containing surfactant. However, it is stated that the thus obtained impression materials are insufficiently hydrophilic, i.e. within a period of 30 seconds after delivery of a drop of water, a contact angle was obtained which was significantly greater than 10°. Compositions containing 0.2% by weight of a non-ionic alkyl-capped fatty alcohol ethoxylate surfactant are said to have only produced impression materials with an acceptable wetting behavior when the composition also contained 0.75% by weight of fluorosurfactant and 0.75% of silicon-containing surfactant or 0.375% by weight of fluorosurfactant and 1.125% by weight of silicon-containing surfactant.
DE 10 2009 021 553 A1 discloses a curable composition comprising curable polymers and also at least one non-ionic or ionic fluorosurfactant selected from a group consisting of eight specific classes of fluorosurfactants, Additionally, the composition may comprise at least one additional fluorosurfactant and/or at least one silicon-containing surfactant having a molar mass of less than 6000 g/mol and/or a polyether containing alkylene residues and/or alkinyl residues and/or a polyether which is hydroxyl and/or aryloxy and/or arylalkyloxy and/or alkoxy-terminated. An upper limit of the surfactant content of the curable composition is not disclosed.
DE 43 06 997 A1 discloses a rubber-elastic composition, for instance a dental impression composition based on vulcanizable polyether materials wherein the composition comprises at least one hydrophilic silicone oil and/or at least one non-ionic surfactant. Regarding the non-ionic surfactant, numerous alternatives from the most different classes of surfactants are proposed, among others fluorinated hydrocarbon compounds as well as alkoxylated fatty alcohols and acylated alkoxylated fatty alcohols. Compositions comprising an alkoxylated fatty alcohol as well as a fluorosurfactant are not disclosed. Any composition described by way of example contains only one single surfactant. In the completely vulcanized and completely polymerized state, the rubber-elastic compositions shall have a 10 second wetting angle of less than 55°, preferably less that 45° and especially less than 35°. The wetting angle of the completely polymerized composition does not allow for any conclusion how well the impression composition wets and flows onto the moist dental substance and oral mucosa which are covered with saliva and possibly blood, when dental impressions are taken, i.e. in the not yet cured state of the impression composition.
WO 2009/079534 A2 discloses a curable dental composition comprising one or more surfactants and a fluorine-containing compound of the formula given there. The surfactant may be for instance a silicon-containing surfactant or an ethoxylated fatty alcohol. Thereby, it was found that dental compositions containing a fluoro-compound as defined in WO 2009/079534 A2 and no surfactant do not show an improved wetting behavior compared to compositions containing a typical fluorosurfactant as, e.g., Zonyl™ FSO-100, while on the other hand dental compositions comprising a fluoro-compound as defined in WO 2009/079534 A2 in combination with a surfactant show an improved wetting behavior.
In dental technology, there is always a need for compositions for dental impression materials which are sufficiently hydrophilic so that when dental impressions are taken, i.e. in the not yet cured state of the impression material, the moist dental substance and oral mucosa which are covered with saliva and possibly blood can be immediately, preferably spontaneously, wetted and the dental impression material can flow directly thereonto so that an impression, accurate in every detail, of the dental situation is obtained.